R-774M (serv.man2). Part 1 Text (1-30) - Sharp Home Appliance Service Manual (repair manual). Page 7

R-774M - 7

Note:

The On/Off time ratio does not exactly correspond
to the percentage of microwave power, because
approx. 3 seconds  is needed for heating up the
magnetron filament.

TOP GRILL (Figure O-3a)
In this condition the food is cooked by the top grill heating
element. Programme the desired cooking time by touch-
ing the TIME keys and touh the GRILL key once. When the
STARTkey is touched, the following operations occur:

1. The numbers on the digital readout start the count

down to zero.

2. The oven lamp, cooling fan motor and turntable motor

are energized.

3. The relay RY3 is energized and the main supply

voltage is applied to the top grill heating element.

4. Now, the food is cooked by the top grill heating ele-

ment.

BOTTOM GRILL (Figure O-3b)
In this condition the food is cooked by bottom grill heating
element energy. Programme the desired cooking time by
touching the TIME keys and touh the GRILL key twice.
When the STARTkey is touched, the following operations
occur:

1. The numbers on the digital readout start the count

down to zero.

2. The oven lamp, cooling fan motor and turntable motor

are energized.

3. The relay RY4 is energized and the main supply

voltage is applied to the bottom grill heating element.

4. Now, the food is cooked by the bottom grill heating

element.

TOP AND BOTTOM GRILL (Figure O-3c)
In this condition the food is cooked by top and bottom grill
heating elements energy. Programme the desired cook-
ing time by touching the TIME keys and touh the GRILL
key three times. When the STARTkey is touched, the
following operations occur:

1. The numbers on the digital readout start the count

down to zero.

2. The oven lamp, cooling fan motor and turntable motor

are energized.

3. The relay RY4 is energized and the main supply

voltage is applied to the bottom grill heating element.

4. The relay RY3 is energized and the main supply

voltage is applied to the top grill heating element.

5. Now, the food is cooked by the top and bottom grill

heating elements.

PRE-HEATING (Figure O-4)
Programme the desired oven temperature by touching
OVEN (˚C) key. When the START key is touched, the
following operations occur:
1. The coil shut-off relays RY1  and RY6 are energized,

the oven lamp, cooling fan motor and turntable motor
are turned on.

2. The coil shut-off relays RY3  and RY4 are energized by

the control unit and the mains supply voltage is applied
to the top and bottom heating elements.

3. When the oven temperature reaches the selected pre-

heat temperature,  the following operations occur:

3-1. The coil shut-off relays RY3  and RY4 are de-ener-

gised by control unit temperature circuit and thermis-
tor, switching to the top and bottom grill heating
elements off.

3-2. The oven will then continue to function for 30 minutes,

turning the top and bottom heating elements on and
off, as needed to maintain the selected pre-heat
temperature. The oven will shut-down completely
after 30 minutes.

NOTE: The fan motor will be turned on and off at

preheating. And the convection motor will be turned
off at  preheating. See "Power setting" on page 9.

OVEN COOKING (Figure O-4)
When the pre-heat temperature is reached, a beep signal
will sound indicating that the holding temperature has
been reached in the oven cavity. Open the door and place
the food to cooked in the oven. Program desired cooking
time by touching the TIME keys and program oven tem-
perature by touching the OVEN (˚C) key . When the
START key is touched, the following operations occur:
1. The numbers on the digital readout start the count

down to zero.

2. The oven lamp, cooling fan motor and turntable motor

are energized.

3. The relays RY3  and RY4 are energized (if the cavity

temperature is lower than selected temperature) and
the mains supply voltage is applied to the top and
bottom heating elements to return to the selected
cooking temperature.

4. Upon completion of the cooking time, the audible sig-

nal will sound, and the oven lamp, turntable motor,
cooling fan motor, top and bottom heating elements
are de-energized. At the end of cooking cycle, if the
cavity air temperature rises above 120˚C, the power to
the relay RY6 will be maintained (by the thermistor
circuit) to continue operation of the cooling fan motor
until the temperature drops below 105˚C. At that time
the relay RY6 will be de-energized, turning off the fan
motor.

MICROWAVE AND TOP GRILL  (Figure O-5a)
Programme the desired cooking time by touching the
TIME keys. Touch the DUAL GRILLL key once. Select the
microwave power level by touching the MICROWAVE
POWER LEVEL key. When the STARTkey is touched, the
following operations occur:

1. The numbers on the digital readout start the count

down to zero.

2. The oven lamp, cooling fan motor and turntable motor

are energized.

3. The relay RY3 is energized and the main supply

voltage is applied to the top grill heating element.

4. The relay RY2 is energized and microwave energy is